1. Field of the Invention
The present invention relates to a magnetoresistance effect element suitable for use as a magnetic head and the like, and a magnetic recording apparatus where the magnetoresistance effect element is employed as a magnetic head.
2. Description of the Related Art
Recently, spin valve type magnetoresistance effect elements where resistance change by a magnetic field is extremely large (e.g., Phys. Rev. B., 43 (1991) 1297) are proposed instead of magnetoresistance effect elements where anisotropic magnetoresistance effect of a single-layer magnetic film is used. The spin valve type magnetoresistance effect elements have a pair of ferromagnetic layers separated by a non-magnetic metallic thin film (e.g., a Cu thin film) with a thickness of about 2 to 5 nm and an anti-ferromagnetic layer laminated on one of the ferromagnetic layers. Illustrative ferromagnetic layers include a NiFe alloy film and a Co film where the thickness of a unit ferromagnetic layer is about 5 to 10 nm. Illustrative anti-ferromagnetic layers include a FeMn alloy film.
In such a structure, while magnetization of a ferromagnetic layer which contacts an anti-ferromagnetic layer is fixed, only magnetization direction of a ferromagnetic layer which does not contact an anti-ferromagnetic layer varies. As a result, a state where magnetization of upper and lower ferromagnetic layers are parallel, and a state where the magnetization are antiparallel can be realized. A large change in resistance between both the states can be obtained by spin-dependent scattering.
In order to increase the resistance change sensitivity (%(A/m)) of the above-described spin valve type magnetoresistance effect elements, it is important that the resistance change ratio is increased and this change occurs on a magnetic field side as low as possible.
As a means for increasing the resistance change ratio itself, it is known that a middle non-magnetic metallic layer is made to be as thin as possible to increase the number of electrons moving between both the ferromagnetic layers without scattering. However, in conventional spin valve type magnetoresistance effect elements, if the thickness of a middle non-magnetic metallic layer made of e.g., Cu is 2 nm or less, the exchange coupling between the upper and lower ferromagnetic layers becomes stronger and it is difficult to change the angle formed by magnetization of both the ferromagnetic layers in a low magnetic field. Thus, even if the resistance change ratio itself is increased, the resistance change sensitivity cannot be enhanced.